Saving with 6abc: Sell your old iPhone sooner, rather than later

If you're planning to get a new iPhone 6, and you want to get some money for your older model iPhone, you'll want to act quickly.

According to a recent study by uSell.com, the value of your old phone will decline rapidly:

* two weeks after a new iPhone launch, old iPhones lose about 11% in value.

* four weeks after launch, old iPhones depreciate about 15%.

* six weeks after launch, old iPhones depreciate about 18%.

* By week seven, old phones are worth about 21% less.